Automatic power control (APC) of light emitting devices allows for a constant and a consistent output from these devices. Generally, automatic power control of edge emitting laser devices is easily achieved because edge emitting devices emit light from two ends. Thus, enabling one of the light emitting ends to be used to measure the power output, which is subsequently use to adjust the power input to the edge emitting device, thereby adjusting the power output.
However, automatic power control of a vertical cavity surface emitting laser (VCSEL) having a wavelength of less than 875 nm is a difficult task because the gallium arsenide (GaAs) VCSEL substrate is absorptive to the band width emission, thus making measurement of the output and subsequent adjustment thereof a difficult task. Conventionally, in order to accomplish this task, several optical devices, such as photodiodes or photodetectors, mirrors, beam splitters, and the like are positioned manually in the optical path of the emission from the VCSEL. With the optical devices being positioned manually, several problems or disadvantages result, such as a high cost of manufacture, a lack of repeatability, and poor quality control.
In addition, in scanning type optical data storage, such as tape based rapid access data storage systems, VCSELs are typically used as the light source. The problem arises in the reading of recorded media on the data storage device, such as a CD or DVD. Typically, a photodetector, or detecting array, separately fabricated from that of the VCSEL is utilized to detect a return signal from the recorded media, which leads to a complex pickup head design. This presents an even greater problem when an array of VCSELs is used for parallel data reading.
During operation, when a focused light beam hits the recorded media, the beam is diffracted back toward the lens and pickup system. The diffracted beam is a SinC function, meaning the light is diffracted back as a center 0 order mode and two side lobes that are .+-.1 order mode. The 0 order mode will trace back the original path of the incident beam with identical geometric dimension. The .+-.1 order modes have a larger divergence angle, and will be collimated by the focal lens back toward the original light source, but with a larger dimension.
Accordingly, it can be readily seen that conventional VCSELs and signal detection from recorded media has several disadvantages and problems, thus not enabling their manufacture in a compact form. Therefore, an integrated article and method for making same that simplifies the fabrication process, reduces cost, and improves reliability would be highly desirable.
It is a purpose of the present invention to provide a new and improved integrated VCSEL and photodetectors for automatic power control (APC) of the VCSEL emission and return signal detection in a data storage read mode.
It is another purpose of the present invention to provide a new and improved integrated VCSEL and photodetectors which are simple and relatively inexpensive to manufacture.
It is still another purpose of the present invention to provide a new and improved integrated VCSEL and photodetectors which are integrated with a minimum of labor and cost.
It is a further purpose of the present invention to provide a new and improved integrated VCSEL and photodetector which can be utilized to control the output of the VCSEL and detection of RF signals in a read mode.